"Coiled tubing" is now routinely used as a workstring in carrying out various operations in certain wellbores. As commonly used in the art, the term "coiled-tubing" or "reeled tubing" refers to a long, continuous length of a relatively small-diameter, thin-walled steel tubing which is wound onto and off of a large-diameter reel. The reel, in turn, can be mounted onto a trailer or the like so that it can be moved from site to site when needed. Once the reel is positioned at a work site (e.g. a wellhead), the continuous tubing is paid off the reel and down the well to carry out the desired operation (e.g. treating a formation, washing a liner, drilling a lateral wellbore, etc.). Upon completion of the operation, the coiled tubing is withdrawn and rewound onto the reel for reuse as needed.
In a typical, coiled-tubing application, the tubing is fed from the reel and through a relatively large-diameter guide arch to an injector head or the like which, in turn, grips the tubing and spools it on or off the reel while at the same time physically feeding it into or out of the wellbore. It is important to maintain the tubing in a proper arch between the reel and the injector head in order not to crimp or otherwise damage the tubing and to insure smooth feeding of the tubing. To do this, the tubing is usually passed over a large-diameter guide or a "gooseneck" which is positioned between the reel and the injector head to control the bending of the tubing.
Further, it is important to keep the coiled-tubing properly wound in layered coils on the reel during operation and prevent it from prematurely unwinding. That is, steel tubing resists coiling and will "unwind" if left unrestrained much in the same manner as does a tightly-wound mainspring of a watch. Therefore, if the coiled-tubing is not properly constrained on the reel, it is likely to prematurely "unwind" or "spring" the coils of tubing into disarray on the reel thereby causing damage and/or substantial delays while the tubing has to be untangled and rewound onto the reel. Most known coiled-tubing systems restrain the tubing on the reel and prevent it from prematurely "unwinding" by adjusting the tension of the tubing on the reel against the force from an injector while spooling the tubing or by a mechanical braking mechanism or the like during transit and/or non-use.